This invention relates to an image recording apparatus and an apparatus for recording an image for medical use (hereinafter referred to as a medical-use image recording apparatus for simplicity's sake), which carry out recording on a recording medium or display on the basis of image information, as well as a system for an image for medical use carrying out the processing of an image (hereinafter referred to as a medical-use imaging system for simplicity's sake), and in particular, to an image recording apparatus and a medical-use image recording apparatus as well as a medical-use imaging system which practice the ink jet recording of image information for medical use obtained by an input apparatus such as a medical-use image radiographing apparatus.
In recent years, it has been put into practice to devise a method for obtaining the information of a medical-use radiation image without the use of a radiographic film composed of silver halide photosensitive material. For example, it has broadly been spreading a radiation image reading apparatus which uses an imaging plate mainly composed of a stimulable phosphor, once stores a radiation image, and after that, takes out the image as stimulated emission of light by the use of an excitation light, to obtain an image signal by the photoelectric conversion of the stimulated emission of light (an apparatus of Computed Radiography hereinafter abbreviated as CR).
Further, lately, also it has been proposed an apparatus for reading radiation image information by the combination of a radiation phosphor or a radiation photoconductor with a two-dimensional semiconductor detector such as a TFT switching device (a Flat Panel Detector hereinafter abbreviated as an FPD).
Further, also it has been spreading a radiation image input apparatus other than a simple X-ray radiographing apparatus such as an X-ray computed tomography apparatus (X-ray CT apparatus) and a magnetic resonance imaging apparatus (an MRI apparatus). These medical-use image input apparatus provide image information in a form of a digital signal in most cases.
In diagnosing these images for medical use, it is mostly used a method in which image information is recorded on a transmission recording medium and/or reflection recording medium and observed in a form of a hard copy. For a medical-use image recording apparatus which records medical-use image information on a recording medium, it is often used an apparatus employing a method in which an image is recorded by exposing a transmission recording medium using a silver halide recording material to a laser beam. By this method, a monochromatic image having multiple gray scales can be depicted with an excellent gradation characteristic, and on top of it, a high diagnosis capability can be exhibited by the observation of the image recorded on a transmission medium using a transmission light.
Besides, lately, expectation is placed on the possibility of recording a medical-use image by means of a recording apparatus of an ink jet type.
It is desirable that the above-mentioned medical-use image recording apparatus expresses image information obtained by a radiation image input apparatus with a fidelity as high as possible, but actually, an image blur peculiar to the recording apparatus is produced.
For example, in a method in which an image is recorded by a laser beam exposure, an image blur resulting from the laser beam having a diameter of a certain size is produced. Further, in what is called a thermal recording method, in which an image is recorded by the application of heat to each of the pixels of the recording medium, an image blur resulting from the thermal head having a finite size and the heat spreading is produced. Further, also in an ink jet method, an image blur due to it that the coloring agent in the ink runs to spread inside the recording medium or on the surface.
Further, also in a display monitor such as a CRT or a liquid crystal display, an image blur is produced. Such an image blur brings about the lowering of diagnosis capability, and possibly it results in a diagnosis error.
As regards the above-mentioned image blur, its degree becomes different with the change of the medical-use image recording apparatus; further, in some cases, even in the one and same medical-use image recording apparatus, the degree of image blur becomes different in accordance with the density of an image to be recorded, which prevents the diagnosis from being performed on the basis of a stable image quality.
In order to make these kinds of image blur small, in a laser exposure method for example, it is appropriate to make the diameter of the laser beam smaller; however, there has been a problem that the optical system became of high cost and unevenness in recording occurred which lowered the image quality on the contrary. Further, also in an ink jet method, in order to make the diameter of ink dots smaller, it is appropriate to make smaller the ink drops to be jetted; however, the technology for making it is difficult, and also there has been a problem that, with the liquid drops being made smaller, the recording speed became lowered.
Further, in recording an image by an ink jet method, in some cases ink deposition amount onto a recording medium becomes different in accordance with the density of an image to be recorded. Depending on the ink deposition amount on the recording medium, mobility of the dye material in the recording medium becomes different, and owing to it, the degree of spreading, that is, the sharpness characteristic becomes different. Hence, there has been a problem that the sharpness characteristic became different in accordance with the density of an image to be recorded which made it impossible to obtain a stable image quality.
This invention has been made in view of the above-mentioned points of problem, and its object is to provide an image recording apparatus and a medical-use image recording apparatus which are capable of recording an image having no image blur and a high diagnosis capability in a simple method.
Further, it is another object of this invention to actualize a medical-use imaging system which is not influenced by the change of the density of an image to be recorded, and the change of the image recording apparatus and/or image display apparatus, and is capable of providing an image having a stable image quality.